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Researchers have developed a technique that uses sensors and computational software to monitor forces exerted on wind turbine blades, a step toward improving efficiency by adjusting for rapidly changing wind conditions.
The research by engineers at Purdue University and Sandia National Laboratories is part of an effort to develop a smarter wind turbine structure.
“The ultimate goal is to feed information from sensors into an active control system that precisely adjusts components to optimize efficiency,” says Purdue doctoral student Jonathan White (pictured below), who is leading the research with Douglas Adams, who directs Purdue’s Center for Systems Integrity.
The system also could help improve wind turbine reliability by providing real-time information to control systems to prevent catastrophic wind turbine damage from high winds.
The engineers embedded sensors called uniaxial and triaxial accelerometers inside a wind turbine blade as the blade was being built. The blade is now being tested on a research wind turbine at a U.S. Department of Agriculture test site in Texas.
Such sensors could be instrumental in future turbine blades that have control surfaces and simple flaps like those on an airplane’s wings to change the blade’s aerodynamic characteristics for better control. Because these flaps would be changed in real time to respond to changing winds, constant sensor data would be critical.
Research findings show that using a trio of sensors and “estimator model” software developed by White accurately reveals how much force is exerted on the blades. Purdue and Sandia have applied for a provisional patent on the technique.
The sensors are capable of measuring acceleration occurring in various directions, which is necessary to accurately characterize the blade’s bending and twisting and small vibrations near the tip that eventually cause fatigue and possible failure. The sensors also measure two types of acceleration. One type—dynamic acceleration—results from gusting winds. The other—called static acceleration—results from gravity and steady background winds. Accurately measuring both forms of acceleration is critical to estimate forces exerted on the blades.
Traveling Wave Reactor
Refueling is a regularly recurring bother for the nuclear power industry. A group of researchers at Intellectual Ventures, an invention and investment company in Bellevue, Wash., have designed a reactor requiring only a small amount of enriched fuel that could run for decades without refueling.
Called a travelingwave reactor, MIT Technology Review says the idea was first proposed in the 1990s. Nuclear reactors based on such designs theoretically could run for more than a century, the publication quotes John Gilleland, manager of nuclear programs, as saying.
Conventional reactors use uranium-235, which must be separated from the more common, nonfissile uranium-238 in special enrichment plants. Every 18 to 24 months, the reactor must be opened, fuel bundles exchanged and the remainder reshuffled to supply all the fissile uranium needed for the next run.
By contrast the traveling-wave reactor needs only a thin layer of enriched U-235. Most of the core is U-238. The reactor itself convertsthe uranium-238 into a usable fuel, plutonium-239. An active region less than one meter thick moves along the reactor core, breeding new plutonium in front of it.
Intellectual Ventures has patented the technology and says it is in licensing discussions with reactor manufacturers but wouldn’t name them.
Worth the Investment?
EPRI is launching a project to provide information that may help a utility conduct a market-based assessment of how much investment its retrofit candidates can support (measured in dollars per kilowatt) and how a unit’s investment worthiness may change with respect to climate policy choices and natural gas prices.
Engineering and technology assessments are necessary to assess the retrofit cost, but the owner must also assess the unit’s role in its power market and how that role changes with climate policy or with swings in natural gas prices. Currently it is not clear how stringent the national policy to limit CO2 emissions may turn out to be. Retrofit costs under an aggressive policy could completely undercut the benefits of keeping a unit compliant.
Analysis will be based on EPRI’s Regional Power Market Analysis framework, which is used to evaluate the effects of climate policy and the individual utility level. It entails a detailed bottom-up simulation of a regional power market. EPRI works with the participating utility to specify its generation, mix, candidate units for retrofit investment, regional power market and key planning and financial analysis assumptions. Relevant climate policy and fuel price scenarios are also identified.
Projects are expected to take four months to complete, with interim results available in the second month. For more information, contact Victor Niemeyer, niemeyer@epri.com.
